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<body>
<div class="document" id="tcl8-bindings-for-xapian">
<h1 class="title">Tcl8 bindings for Xapian</h1>

<p>The Tcl8 bindings for Xapian are packaged in the <tt class="docutils literal">xapian</tt> namespace,
and largely follow the C++ API, with the following differences and
additions. Tcl8 strings and lists, etc., are converted automatically
in the bindings, so generally it should just work as expected.</p>
<p>The <tt class="docutils literal">examples</tt> subdirectory contains examples showing how to use the
Tcl8 bindings based on the simple examples from <tt class="docutils literal"><span class="pre">xapian-examples</span></tt>:
<a class="reference external" href="examples/simpleindex.tcl">simpleindex.tcl</a>,
<a class="reference external" href="examples/simplesearch.tcl">simplesearch.tcl</a>,
<a class="reference external" href="examples/simpleexpand.tcl">simpleexpand.tcl</a>.</p>
<div class="section" id="unicode-support">
<h1>Unicode Support</h1>
<p>In Xapian 1.0.0 and later, the Xapian::Stem, Xapian::QueryParser, and
Xapian::TermGenerator classes all assume text is in UTF-8.  Tcl8 uses
UTF-8 as its internal representation, except that ASCII nul (character value
0) is represented as the overlong (and thus invalid) UTF-8 sequence
<tt class="docutils literal">\xc0\x80</tt>.  We don't currently convert this to/from
<tt class="docutils literal">\x00</tt> so you should avoid passing strings containing ASCII nul
between Tcl and Xapian.</p>
</div>
<div class="section" id="destructors">
<h1>Destructors</h1>
<p>To destroy an object <tt class="docutils literal">obj</tt>, you need to use one of
<tt class="docutils literal">obj <span class="pre">-delete</span></tt> or <tt class="docutils literal">rename obj &quot;&quot;</tt>
(either should work, but see below).</p>
<p>SWIG's Tcl wrapping doesn't handle an object returned by a factory function
correctly.  This only matters for the Xapian::WritableDatabase class, and we
avoid wrapping the problematic <tt class="docutils literal"><span class="pre">Xapian::Chert::open</span></tt> factory function to
avoid setting a trap for the unwary.
You can just use a <tt class="docutils literal"><span class="pre">Xapian::WritableDatabase</span></tt> constructor
instead (and specify a backend by passing <tt class="docutils literal"><span class="pre">$::xapian::DB_BACKEND_GLASS</span></tt> or
similar in the flags).</p>
<p>As of Xapian 1.1.0, you can explicitly close the database, so the lack
of a call to the destructor isn't an issue:</p>
<pre class="literal-block">
xapian::WritableDatabase xapiandb testdir $::xapian::DB_CREATE_OR_OVERWRITE
xapian_db close
</pre>
<p>If you want compatibility with Xapian 1.0.x, then
Michael Schlenker reports that this form works (i.e. the destructor gets
called):</p>
<pre class="literal-block">
xapian::WritableDatabase xapiandb testdir $::xapian::DB_CREATE_OR_OVERWRITE
rename xapiandb &quot;&quot;
</pre>
<p>However, apparently none of these forms work:</p>
<pre class="literal-block">
xapian::WritableDatabase xapiandb testdir $::xapian::DB_CREATE_OR_OVERWRITE
set db xapiandb
$db -delete

set db [xapian::WritableDatabase xapiandb testdir $::xapian::DB_CREATE_OR_OVERWRITE]
$db -delete

set db [xapian::WritableDatabase xapiandb testdir $::xapian::DB_CREATE_OR_OVERWRITE]
rename $db &quot;&quot;
</pre>
</div>
<div class="section" id="exceptions">
<h1>Exceptions</h1>
<p>Xapian::Error exceptions can be handled in Tcl like so:</p>
<pre class="literal-block">
if [catch {
    # Code which might throw an exception.
  } msg] {
    # Code to handle exceptions.
    # $errorCode is &quot;XAPIAN &lt;error_class&gt;&quot; (e.g. &quot;XAPIAN DocNotFoundError&quot;.)
    # $msg is the result of calling get_msg() on the Xapian::Error object.
}
</pre>
</div>
<div class="section" id="iterators">
<h1>Iterators</h1>
<p>All iterators support <tt class="docutils literal">next</tt> and <tt class="docutils literal">equals</tt> methods
to move through and test iterators (as for all language bindings).
MSetIterator and ESetIterator also support <tt class="docutils literal">prev</tt>.</p>
</div>
<div class="section" id="iterator-dereferencing">
<h1>Iterator dereferencing</h1>
<p>C++ iterators are often dereferenced to get information, eg
<tt class="docutils literal">(*it)</tt>. With Tcl8 these are all mapped to named methods, as
follows:</p>
<table border="1" class="docutils">
<caption>Iterator deferencing methods</caption>
<colgroup>
<col width="45%" />
<col width="55%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head">Iterator</th>
<th class="head">Dereferencing method</th>
</tr>
</thead>
<tbody valign="top">
<tr><td>PositionIterator</td>
<td><tt class="docutils literal">get_termpos</tt></td>
</tr>
<tr><td>PostingIterator</td>
<td><tt class="docutils literal">get_docid</tt></td>
</tr>
<tr><td>TermIterator</td>
<td><tt class="docutils literal">get_term</tt></td>
</tr>
<tr><td>ValueIterator</td>
<td><tt class="docutils literal">get_value</tt></td>
</tr>
<tr><td>MSetIterator</td>
<td><tt class="docutils literal">get_docid</tt></td>
</tr>
<tr><td>ESetIterator</td>
<td><tt class="docutils literal">get_term</tt></td>
</tr>
</tbody>
</table>
<p>Other methods, such as <tt class="docutils literal"><span class="pre">MSetIterator::get_document</span></tt>, are
available under the same names.</p>
</div>
<div class="section" id="mset">
<h1>MSet</h1>
<p>MSet objects have some additional methods to simplify access (these
work using the C++ array dereferencing):</p>
<table border="1" class="docutils">
<caption>MSet additional methods</caption>
<colgroup>
<col width="44%" />
<col width="56%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head">Method name</th>
<th class="head">Explanation</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="docutils literal">mset get_hit index</tt></td>
<td>returns MSetIterator at index</td>
</tr>
<tr><td><tt class="docutils literal">mset get_document_percentage index</tt></td>
<td><tt class="docutils literal">mset convert_to_percent [mset get_hit index]</tt></td>
</tr>
<tr><td><tt class="docutils literal">mset get_document index</tt></td>
<td><tt class="docutils literal">[mset get_hit index] get_document</tt></td>
</tr>
<tr><td><tt class="docutils literal">mset get_docid index</tt></td>
<td><tt class="docutils literal">[mset get_hit index] get_docid</tt></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="non-class-functions">
<h1>Non-Class Functions</h1>
<p>The C++ API contains a few non-class functions (the Database factory
functions, and some functions reporting version information), which are
wrapped like so for Tcl:</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">Xapian::version_string()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::version_string</span></tt></li>
<li><tt class="docutils literal"><span class="pre">Xapian::major_version()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::major_version</span></tt></li>
<li><tt class="docutils literal"><span class="pre">Xapian::minor_version()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::minor_version</span></tt></li>
<li><tt class="docutils literal"><span class="pre">Xapian::revision()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::revision</span></tt></li>
<li><tt class="docutils literal"><span class="pre">Xapian::Auto::open_stub()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::open_stub</span></tt> (now deprecated)</li>
<li><tt class="docutils literal"><span class="pre">Xapian::Chert::open()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::chert_open</span></tt> (but note that the WritableDatabase version isn't wrapped - see the 'Destructors' section above for an explanation - and this function is deprecated anyway).</li>
<li><tt class="docutils literal"><span class="pre">Xapian::InMemory::open()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::inmemory_open</span></tt> (now deprecated)</li>
<li><tt class="docutils literal"><span class="pre">Xapian::Remote::open()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::remote_open</span></tt> (both the TCP and &quot;program&quot; versions are wrapped - the SWIG wrapper checks the parameter list to decide which to call).</li>
<li><tt class="docutils literal"><span class="pre">Xapian::Remote::open_writable()</span></tt> is wrapped as <tt class="docutils literal"><span class="pre">xapian::remote_open_writable</span></tt> (both the TCP and &quot;program&quot; versions are wrapped - the SWIG wrapper checks the parameter list to decide which to call).</li>
</ul>
</div>
<div class="section" id="constants">
<h1>Constants</h1>
<p>For Tcl, constants are wrapped as <tt class="docutils literal"><span class="pre">$xapian::CONSTANT_NAME</span></tt>
or <tt class="docutils literal"><span class="pre">$xapian::ClassName_CONSTANT_NAME</span></tt>.
So <tt class="docutils literal"><span class="pre">Xapian::DB_CREATE_OR_OPEN</span></tt> is available as
<tt class="docutils literal"><span class="pre">$xapian::DB_CREATE_OR_OPEN</span></tt>, <tt class="docutils literal"><span class="pre">Xapian::Query::OP_OR</span></tt> is
available as <tt class="docutils literal"><span class="pre">$xapian::Query_OP_OR</span></tt>, and so on.</p>
</div>
<div class="section" id="query">
<h1>Query</h1>
<p>In C++ there's a Xapian::Query constructor which takes a query operator and
start/end iterators specifying a number of terms or queries, plus an optional
parameter.  In Tcl, this is wrapped to accept a Tcl list
to give the terms/queries, and you can specify
a mixture of terms and queries if you wish.  For example:</p>
<pre class="literal-block">
set terms [list &quot;hello&quot; &quot;world&quot;]
xapian::Query subq $xapian::Query_OP_AND $terms
xapian::Query bar_term &quot;bar&quot; 2
xapian::Query query $xapian::Query_OP_AND [list subq &quot;foo&quot; bar_term]
</pre>
<div class="section" id="matchall-and-matchnothing">
<h2>MatchAll and MatchNothing</h2>
<p>As of Xapian 1.1.1, these are wrapped for Tcl as
<tt class="docutils literal"><span class="pre">$xapian::Query_MatchAll</span></tt> and
<tt class="docutils literal"><span class="pre">$xapian::Query_MatchNothing</span></tt>.</p>
</div>
</div>
<div class="section" id="enquire">
<h1>Enquire</h1>
<p>There is an additional method <tt class="docutils literal">get_matching_terms</tt> which takes
an MSetIterator and returns a list of terms in the current query which
match the document given by that iterator.  You may find this
more convenient than using the TermIterator directly.</p>
</div>
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